I ordered wheeltop groupset because I was tired of waiting for affordable er9 shipping to Canada. I also thought that I would not have to bother placing the battery in the seatpost!
Yeah, that was my initial recommendation from the beginning, either Wheeltop or SRAM AXS. The ER9/X is doable, but it's extra work and does require some DIY know-how. My other idea would be the new wireless LTwoo eTX with replaceable batteries. I could totally imagine building a 1x climbing frame with a large ratio cassette using that groupset!